Microwave synthesis of high-flux NaY zeolite membranes in fluoride media

High-flux NaY zeolite membranes were synthesized using low-cost mullite supports by microwave heating in fluoride media. Pervaporation and vapor permeation performances of these membranes were evaluated at temperature range of 303-383 K. The thickness of NaY zeolite membrane prepared by microwave heating was thinner than that prepared by conventional heating. Six membranes synthesized by microwave heating displayed fluxes of 3.43 ± 0.13 kg (m² h)^-1 and separation factors 1300 ± 390 for a 95 wt% n-butanol aqueous solution at 348 K. The water fluxes of these membranes were 60-80% higher than those of NaY membranes prepared by conventional heating. Water fluxes and water/alcohol separation factors of these membranes increased with the increasing kinetic diameter of alcohols for the water/methanol, water/ethanol, water/i-propanol and water/n-butanol binary mixtures. The separations of water/alcohol mixtures through these high-flux membranes were affected by concentration polarization. Increasing flow rates from 9.5 L h^-1 (Reynolds number = 1300, laminar flow state) to 37.8 L h^-1 (Reynolds number = 5200, turbulent flow state) at 363 K decreased the polarization boundary layer, and thus increased membrane flux and membrane selectivity by 26% and 23%, respectively.